Global Governance on the Ground offers a new approach to how international organizations govern. Through an in-depth look at the case of migration and asylum, the book argues that international organizations (IOs) not only govern global challenges through rules, standards, expertise, and numbers but also through practice on the ground. Much scholarship has been devoted to the question of how IOs become autonomous agents and exercise authority to shape governance outcomes. Far less attention has been given to the way IOs use their field access to govern global issues on the ground-without first going through formal policy channels or renegotiating their authority. The book demonstrates that through field-based practice, IOs directly regulate global issues in the spaces where they become virulent, in different locations across the globe. The book draws on ethnographic fieldwork at the European external border, comprising interviews at the headquarters of seven organizations, including the United Nations High Commissioner for Refugees (UNHCR), the International Organization for Migration (IOM), and three humanitarian NGOs. This, combined with an extensive document analysis, shows that field staff improvise to organize collective action on under-regulated issues and that headquarter staff consolidate and diffuse their operational knowledge. The book conceptualizes this governance mode that operates at a low institutional threshold but largely determines the de facto governance of contested or crisis-ridden global problems.